Note 12 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Sales	$ 19,771,137	$ 10,892,868	$ 45,243,029	$ 21,459,809
Gross profit	4,450,222	3,034,379	10,955,241	7,441,039
Operating income	2,471,279	1,414,462	4,931,309	2,989,283
Income (loss) before provision for income taxes	2,087,183	1,294,303	3,111,685	2,494,466
Operating Segments [Member] | Commercial Air Handling [Member]
Sales	9,876,700	7,846,896	29,876,961	11,190,841
Gross profit	2,743,833	1,946,546	7,861,725	2,900,293
Operating income	1,696,934	1,083,140	4,357,970	1,425,524
Income (loss) before provision for income taxes	1,686,296	816,669	4,316,875	1,424,878
Operating Segments [Member] | Test and Measurement [Member]
Sales	790,297	1,560,696	2,786,742	5,783,621
Gross profit	130,293	533,879	722,062	3,233,133
Operating income	130,293	41,816	(239,151)	707,126
Income (loss) before provision for income taxes	130,293	188,128	(94,828)	628,275
Operating Segments [Member] | Industrial Hose [Member]
Sales	1,718,138	1,485,276	5,193,324	4,485,347
Gross profit	356,000	553,954	1,151,358	1,307,613
Operating income	111,419	289,506	413,573	856,633
Income (loss) before provision for income taxes	48,454	289,506	272,608	441,313
Operating Segments [Member] | Aerospace [Member]
Sales	7,386,002		7,386,002
Gross profit	1,220,096		1,220,096
Operating income	706,424		706,424
Income (loss) before provision for income taxes	620,023		620,023
Corporate, Non-Segment [Member]
Operating income	(173,791)		(307,507)
Income (loss) before provision for income taxes	(397,883)		(842,419)
Consolidation, Eliminations [Member]
Income (loss) before provision for income taxes			$ (1,160,574)